The present invention relates to periodic dielectric structures, generally, and more particularly to a device for tuning the propagation of electromagnetic energy.
Numerous applications have been devised for photonic crystals. A photonic crystal exhibits propagating wave characteristics (as described, for example, with a photonic band structure) for controlling the propagation of electromagnetic (xe2x80x9cEMxe2x80x9d) energy therethrough. A photonic crystal is realized by a three-dimensional dielectric structure having periodic variations in its refractive index. These periodic variations may be formed in one-, two- or all three-dimensions of the dielectric structure. As such, a photonic crystal may control the propagation of EM energy, in any direction, through the periodic dielectric structure.
One application of increasing interest for photonic crystals is a device for controlling the propagation of EM energy. The propagating wave characteristics of a periodic dielectric structure may include a photonic bandgap, for a specific orientation (i.e., direction) of the propagation of the received EM energy. A photonic bandgap suppresses a band of wavelengths from propagating through a photonic crystal. Photonic crystals and their periodic dielectric structures, however, are static elements. A periodic dielectric structure""s propagating wave characteristics and photonic bandgap are fixed. Consequently, the propagating wave characteristics may not be altered without modifying the periodic dielectric structure.
Several solutions have been proposed to alter or tune the propagating wave characteristics of a photonic crystal by modifying the periodic dielectric structure. These solutions heat or stretch the periodic dielectric structure, for example, to arrive at the desired propagating wave characteristics. Heating or stretching the periodic dielectric structure, however, requires too much time for some applications.
Consequently, a demand exists for a device for controlling the propagation of EM energy using a photonic crystal in which the periodic dielectric structure is tuned expeditiously.
In accordance with the present invention, we have solved the aforementioned problems of the prior art by employing a first and a second periodic dielectric structure, one of which is movable with respect to the other. For present purposes, the term movable and its derivatives means mechanically moving, positioning and/or rotating one periodic dielectric structure with respect to the other, in contradistinction to the prior approach of heating or stretching the periodic dielectric structure. Each periodic dielectric structure exhibits propagating wave characteristics. For the purposes of the present invention, the propagating wave characteristics of periodic dielectric structure include, but are not limited to reflectivity, transmissivity, waveguiding, and refractive index. By aligning one periodic dielectric structure with the other periodic dielectric structure, a resultant or composite propagating wave characteristic is created. Consequently, as one dielectric structure is moved with respect to the other, the composite propagating wave characteristic is altered.